แก้ไข

แชร์ผ่าน

SQLDriverToDataSource Function

  • บทความ

SQLDriverToDataSource supports translations for ODBC drivers. This function is not called by ODBC-enabled applications; applications request translation through SQLSetConnectAttr. The driver associated with the ConnectionHandle specified in SQLSetConnectAttr calls the specified DLL to perform translations of all data flowing from the driver to the data source. A default translation DLL can be specified in the ODBC initialization file.

Syntax

  
BOOL SQLDriverToDataSource(  
     UDWORD     fOption,  
     SWORD      fSqlType,  
     PTR        rgbValueIn,  
     SDWORD     cbValueIn,  
     PTR        rgbValueOut,  
     SDWORD     cbValueOutMax,  
     SDWORD *   pcbValueOut,  
     UCHAR *    szErrorMsg,  
     SWORD      cbErrorMsgMax,  
     SWORD *    pcbErrorMsg);

Arguments

fOption
[Input] Option value.

fSqlType
[Input] The ODBC SQL data type. This argument tells the driver how to convert rgbValueIn into a form acceptable by the data source. For a list of valid SQL data types, see SQL Data Types.

rgbValueIn
[Input] Value to translate.

cbValueIn
[Input] Length of rgbValueIn.

rgbValueOut
[Output] Result of the translation.

Note

The translation DLL does not null-terminate this value.

cbValueOutMax
[Input] Length of rgbValueOut.

pcbValueOut
[Output] The total number of bytes (excluding the null-termination byte) available to return in rgbValueOut.

For character or binary data, if this is greater than or equal to cbValueOutMax, the data in rgbValueOut is truncated to cbValueOutMax bytes.

For all other data types, the value of cbValueOutMax is ignored and the translation DLL assumes that the size of rgbValueOut is the size of the default C data type of the SQL data type specified with fSqlType.

The pcbValueOut argument can be a null pointer.

szErrorMsg
[Output] Pointer to storage for an error message. This is an empty string unless the translation failed.

cbErrorMsgMax
[Input] Length of szErrorMsg.

pcbErrorMsg
[Output] Pointer to the total number of bytes (excluding the null-termination byte) available to return in szErrorMsg. If this is greater than or equal to cbErrorMsg, the data in szErrorMsg is truncated to cbErrorMsgMax minus the null-termination character. The pcbErrorMsg argument can be a null pointer.

Returns

TRUE if the translation was successful, FALSE if the translation failed.

Comments

The driver calls SQLDriverToDataSource to translate all data (SQL statements, parameters, and so on) passing from the driver to the data source. The translation DLL might not translate some data, depending on the data's type and the purpose of the translation DLL. For example, a DLL that translates character data from one code page to another ignores all numeric and binary data.

The value of fOption is set to the value of vParam specified by calling SQLSetConnectAttr with the SQL_ATTR_TRANSLATE_OPTION attribute. It is a 32-bit value that has a specific meaning for a given translation DLL. For example, it could specify a certain character set translation.

If the same buffer is specified for rgbValueIn and rgbValueOut, the translation of data in the buffer will be performed in place.

Although cbValueIn, cbValueOutMax, and pcbValueOut are of the type SDWORD, SQLDriverToDataSource does not necessarily support huge pointers.

If SQLDriverToDataSource returns FALSE, data truncation might have occurred during translation. If pcbValueOut (the number of bytes available to return in the output buffer) is greater than cbValueOutMax (the length of the output buffer), then truncation occurred. The driver must determine whether or not the truncation was acceptable. If truncation did not occur, the SQLDriverToDataSource returned FALSE due to another error. In either case, a specific error message is returned in szErrorMsg.

For more information about translating data, see Translation DLLs.

For information about See
Translating data returned from the data source SQLDataSourceToDriver
Returning the setting of a connection attribute SQLGetConnectAttr
Setting a connection attribute SQLSetConnectAttr